Nuke the blobstore code, replace with cloud_blobstore library. (#567)

Need the blobstore code elsewhere, so it makes sense to library-ize it.

dss/api/bundles.py

@@ -5,10 +5,10 @@
 
 import iso8601
 import requests
+from cloud_blobstore import BlobNotFoundError
 from flask import jsonify, make_response
 
 from .. import DSSException, dss_handler
-from ..blobstore import BlobNotFoundError
 from ..config import Config
 from ..hcablobstore import BundleFileMetadata, BundleMetadata, FileMetadata
 from ..util import UrlBuilder

dss/api/files.py

@@ -3,19 +3,17 @@
 import json
 import re
 import typing
-
-import chainedawslambda.aws
 from enum import Enum, auto
 
 import iso8601
 import requests
-
+import chainedawslambda.aws
+from cloud_blobstore import BlobAlreadyExistsError, BlobNotFoundError, BlobStore
+from cloud_blobstore.s3 import S3BlobStore
 from flask import jsonify, make_response, redirect, request
 from werkzeug.exceptions import BadRequest
 
 from .. import DSSException, dss_handler
-from ..blobstore import BlobAlreadyExistsError, BlobNotFoundError, BlobStore
-from ..blobstore.s3 import S3BlobStore
 from ..config import Config
 from ..events.chunkedtask import s3copyclient
 from ..hcablobstore import FileMetadata, HCABlobStore

dss/api/subscriptions.py

@@ -8,14 +8,14 @@
 import iso8601
 import requests
 
+from cloud_blobstore import BlobNotFoundError
 from elasticsearch import Elasticsearch
 from elasticsearch.exceptions import ElasticsearchException, NotFoundError
 from elasticsearch_dsl import Search
 from flask import jsonify, make_response, redirect, request
 from werkzeug.exceptions import BadRequest
 
 from .. import Config, Replica, ESIndexType, ESDocType, get_logger
-from ..blobstore import BlobNotFoundError
 from ..error import DSSException, dss_handler
 from ..hcablobstore import FileMetadata, HCABlobStore
 from ..util.es import ElasticsearchClient, get_elasticsearch_index